NF

The presence of multiple neurofibromas is an important diagnostic sign of NF. Single neurofibromas may occasionally occur in people who do not have NF. The number of neurofibromas varies widely among affected individuals from only a few to thousands. There is no way at present to predict how many neurofibromas a person will develop. Dermal neurofibromas rarely, if ever, become cancerous. Such a change, called a malignant transformation, may occur, although very rarely, in plexiform tumors. Therefore, it is important that patients be in the care of an NF specialist. NF is an extremely variable disorder. The severity of NF ranges from extremely mild cases in which the only signs of the disorder in adulthood may be multiple café-au-lait spots and a few dermal neurofibromas, to more severe cases in which one or more serious complications may develop. The complications of NF are discussed in the next section. There is no way to predict who will have a mild case and who will develop serious complications. The majority of people with NF (probably 60%) have mild forms of the disorder. Another 20% have correctable problems and another 20% have serious and persistent problems. Many of the serious problems in NF mentioned below are evident at birth or develop prior to adolescence. These may include congenital defects of the bone, scoliosis, optic glioma and neurological impairment leading to learning disability or mental retardation. People with NF who have reached adulthood without having these problems are unlikely to develop them. Some neurofibromas, depending on their location and size, can be removed surgically if they become painful or infected, or cosmetically troublesome. A new tumor sometimes appears where one has been removed, particularly if that tumor was not removed completely. There is no evidence that removal of growths will increase the rate of appearance of new growths, or can cause incompletely removed tumors to change from benign to cancerous. Café-au-lait spots, the most common sign of NF, are the flat, pigmented spots on the skin, which are called by the French term for coffee (café) with milk (lait) because of their light tan color. In darker-skinned people, café-au-lait spots appear darker in color than surrounding skin. People with NF almost always have six or more café-au-lait spots. (Fewer café-au-lait spots may occur in people who do not have NF; in fact, about 10% of the general population has one or two café-au-lait spots). The size of the spots that identify NF varies from 1/4 inch (5 mm) in children and 3/4 inch (15 mm) in adults to several inches in diameter or larger. In general, with few exceptions, tumors are not more likely to appear where there are spots. Café-au-lait spots are usually present at birth in children who have NF or, generally, appear by two years of age. The number of spots may increase in childhood and occasionally later in life. The spots may be very light in color in infants and usually darken as the child gets older. Smaller pigmented spots, which may be difficult to distinguish from ordinary freckles, may also be present in people with NF. In those who do not have NF, freckling usually occurs in areas of skin exposed to sun. With NF, café-au-lait spots and freckling are present in other areas as well, including the armpit (axilla), where small spots are called axillary freckling, and the groin. Axillary freckling is not seen in every person with NF, but when present it is considered strong evidence of NF. Iris nevi (also called Lisch nodules) are clumps of pigment in the colored part of the eye (iris). Iris nevi, which usually appear around puberty, can be distinguished from iris freckles (commonly seen in people without NF) by a simple and painless procedure called a slit-lamp examination, which is typically performed by an ophthalmologist. Iris nevi do not cause medical problems and do not affect vision. The presence of iris nevi can occasionally be helpful in confirming the diagnosis of NF.